i dont really have any hierarchy suggestions as i do not concern myself with such things but here is a link to see team 190's "hierarchy" :
http://users.wpi.edu/~first/dyn.cgi?node=org you can click on each of the positions there to see a description of what they do; note that a lot of the positions that are there are invisible since they have some correletion to specific robot features which we thought might be "sensetive information"
good luck